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90v/100a DC Power Supply

Lester Thunder

Sep 8, 2016
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Welcome to Electronics Point!


That's pretty ambitious for someone new to electronics.


That's nice, but you have failed to tell us what you are trying to DO. You have told us what you think is how to do it (whatever it may be) by saying "will receive voltage data (what's that?) from sensor arrays (what kind of arrays?) to adjust the speeds of each motor individually." From this I surmise you have three BLDC motors, each with its own speed control, all operating from a 90 V DC power supply of sufficient current capacity to supply all three motors simultaneously with their start-up (locked rotor) current as well as a somewhat lower running current. Is that about it in a nutshell?


The answer is YES. Check out this one available, used, on EBay. This one was apparently sold by Electronic Measurements, Inc. and is called an EMS Power Supply (whatever that is) rated 0 to 100 Volts and 0 to 100 Amps DC, 10 kW output. Requires three-phase power. This type of power supply (with its variable output) is more expensive than a dedicated single-output-voltage power supply, but the price that is asked ($1999.99) is in the right ball park, based on my experience with beasts of this sort.

You could, of course, opt for three separate power supplies, one for each motor. That is what I would do, given the wide range of current demand among three motors. There will be much less, or no interaction, among three voltage-regulated power supplies providing power to three motors versus one voltage-regulated power supply providing power simultaneously to all three motors. The utility wiring is also likely to be less complicated. You should be able to use single phase power, either 120 or 240 VAC, for three power supplies.

The cost of power supplies of equal voltage capability is a function of their output power capability. It may cost a little more for three power supplies whose total power equals or exceeds a single power supply, but there are also advantages. Cost of a spare power supply will be less, and if one supply fails the other two still work. Yada, yada, yada. Buy or build three power supplies is what I would do, given the limited amount of information at hand.


Coming here is a decent start for a newbie in electronics, even if you are an expert in designing large BLDC motors with neodymium rare-earth magnet rotors. i am NOT in such an elite group of designers, but there are others here, @Minder comes to mind, who have extensive practical experience in industrial motor selection, application, and control of same. They need to know what you are trying to DO before they can give you any useful advice on how to do it. All I can offer is advice on power supplies, large and small.

Hop

Hevans1944, this has answered my initial questions exactly. The main reason that I didn't bring the details of the project to full knowledge, here, is that I want to do the prototyping myself....without expertise from more knowledgeable people....so that I can learn. As time progresses, I may ask more questions to dial down into the learning curve. I have a mediocre understanding of motors and I understand the concept on how I want to control them.

And yes, your summation of my question is accurate in that there are 3 independent motors that I'm giving a wide berth on how much power they will require. I'm having a single motor made so that I can wind it myself and run tests to determine which motor will need how much power to perform its required work.

My background is that of an oil refinery operator with software design, but likely not in the language required to code microprocessors....but I am learning that as well.
 

Lester Thunder

Sep 8, 2016
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I am wondering why you passed up the opportunity on using phase vector VFD's and 3 phase motors on 240v 1ph.
If by going to BLDC is because of positioning, then you would need some kind of feedback element such as encoder and controller.
If just velocity control I would have thought VFD's would have done the job.
But there is not all that information as to the application?.
M.
I haven't passed on this as of yet. I just picked the path as the starting point. What information can you offer on the VFD path?
 

Minder

Apr 24, 2015
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From what you have said so far it seems like it is an academic exercise, if so and if you have limited experience resources, I can see it being a very long project, it depends on when and how you need to complete the project.
If considering off the shelf solution at all the VFD may be a consideration, as both VFD and 3 phase motors are common items, and the limit for 1ph operation on 240v of a 3ph VFD/motor combo is around 5hp, which coincides with your limit.
There are three VFD styles, simple velocity, phase vector which reads motor conditions to attempt set rpm as close as possible, and the third which is precise rpm control via encoder feedback.
But note these methods are for mostly rpm control, just with different degrees of accuracy.
M.
 

Tha fios agaibh

Aug 11, 2014
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Either I'm not understanding something or I'm just not explaining correctly

I think you might want to explain what your driving with the motors because there might be a better ways to achieve your goals.

It may make more sense to use gear reduction to meet your torque and Rpm requirements while mitigating the need for high amperage currents.
Or, as Minder suggested; use a Vfd that'd be widely adaptive to various applications.

What Rpm range, torque and duty do you need? Are you limited to 1ph 240v?

Is there a reason your leaning towards bldc motors?
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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Oil refinery operator, huh? I grew up near oil refineries in southwest Louisiana and southeastern Texas, but back in the day it took a boatload of people to run them. I guess everything is computerized and networked today, so just a few people are needed onsite to maybe swap out a flow or temperature sensor and maybe a valve or two...or is it still a complicated operation requiring a lot of hands-on observation and control? Industrial-level chemistry has always fascinated me.
 

Lester Thunder

Sep 8, 2016
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Thr
Oil refinery operator, huh? I grew up near oil refineries in southwest Louisiana and southeastern Texas, but back in the day it took a boatload of people to run them. I guess everything is computerized and networked today, so just a few people are needed onsite to maybe swap out a flow or temperature sensor and maybe a valve or two...or is it still a complicated operation requiring a lot of hands-on observation and control? Industrial-level chemistry has always fascinated me.

There is a much greater level of automation that 20 years ago, but there is still a degree of manning that is required.
 

Lester Thunder

Sep 8, 2016
11
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Messages
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I think you might want to explain what your driving with the motors because there might be a better ways to achieve your goals.

It may make more sense to use gear reduction to meet your torque and Rpm requirements while mitigating the need for high amperage currents.
Or, as Minder suggested; use a Vfd that'd be widely adaptive to various applications.

What Rpm range, torque and duty do you need? Are you limited to 1ph 240v?

Is there a reason your leaning towards bldc motors?

I'm not sold on BLDC as yet. I'm not sure of motor specific loads/speeds as of yet.
 

Lester Thunder

Sep 8, 2016
11
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Sep 8, 2016
Messages
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From what you have said so far it seems like it is an academic exercise, if so and if you have limited experience resources, I can see it being a very long project, it depends on when and how you need to complete the project.
If considering off the shelf solution at all the VFD may be a consideration, as both VFD and 3 phase motors are common items, and the limit for 1ph operation on 240v of a 3ph VFD/motor combo is around 5hp, which coincides with your limit.
There are three VFD styles, simple velocity, phase vector which reads motor conditions to attempt set rpm as close as possible, and the third which is precise rpm control via encoder feedback.
But note these methods are for mostly rpm control, just with different degrees of accuracy.
M.

Thanks for this direction. I looked online and found a site that sells these VFDs that range in a variety of total current output, but I have a few of questions on this.

1. A 5hp/17a VFD is $600. Would this be much cheaper to build from scratch?
2. Would it be cheaper to build a DC supply @ (x)volts/17 or so amps....and a controller to drive the BLDC motor.

I can have either motor AC or DC built....for me it's more about power supply and control. I'm pretty sure that the controller circuit wouldn't be difficult for me to build (I'm actually excited to get to that part).
 

Minder

Apr 24, 2015
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If you don't yet know the motor load demand you may be oversizing the application.
Building either a BLDC or a VFD of that size is not a trivial task.
Many with extensive experience have struggled with the task.
About the most value for a VFD is the Hitachi, There is the Chinese Hunayang, but with these you get what you pay for in the terms of support and quality.
M.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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Thr


There is a much greater level of automation that 20 years ago, but there is still a degree of manning that is required.
Twenty years ago? I was talking about my observations as a kid from the 1950s, not the 1990s. AFAIK, everything was manual control with analog indicators, and perhaps some Honeywell pneumatic controllers and strip-chart pen-and-ink recorders to track process variables. Heating and cracking crude and using fractional distillation to take off the lighter hydrocarbons isn't complicated until you add synthesis to the mix. But now I am way beyond my level of incompetence and understanding of how this is done on an industrial basis outside of a laboratory environment. Glass retorts, beakers, and such are one thing, hundreds of gallons per hour production is something else entirely. Fascinating though.

It really would help us to help you if you would explain what you are trying to DO with those motors.
 
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